Energy consumption has long been an important issue for mobile terminals in cellular systems. Recent trends in green technology make it important to reduce the energy consumption also for the base stations (BS or NodeB) as the base station power consumption is a non-negligible part of the cost for the operator and excessive power consumption has a negative impact on the environment. Furthermore, the energy consumed as part of the base station operation generates heat, and active cooling (e.g. air conditioning) is typically required to control the temperature of the equipment. Active cooling will further add to the total energy consumption of a base station site. Similar comments apply to other wireless network nodes, such as relays and repeaters.